diff --git a/src/compiler/eachFunction.go b/src/compiler/eachFunction.go
index 44bc00e..9ffa2e9 100644
--- a/src/compiler/eachFunction.go
+++ b/src/compiler/eachFunction.go
@@ -10,7 +10,7 @@ func (r *Result) eachFunction(caller *core.Function, traversed map[*core.Functio
 	call(caller)
 	traversed[caller] = true
 
-	for _, function := range caller.Dependencies {
+	for function := range caller.Dependencies.All() {
 		if traversed[function] {
 			continue
 		}
diff --git a/src/core/CompileDelete.go b/src/core/CompileDelete.go
index b834d06..131a9d0 100644
--- a/src/core/CompileDelete.go
+++ b/src/core/CompileDelete.go
@@ -26,6 +26,6 @@ func (f *Function) CompileDelete(root *expression.Expression) error {
 	f.BeforeCall()
 	f.Label(asm.CALL, asm.Label{Name: "mem.free", Type: asm.FunctionLabel})
 	f.AfterCall(f.CPU.Input[:2])
-	f.Dependencies = append(f.Dependencies, free)
+	f.Dependencies.Add(free)
 	return nil
 }
diff --git a/src/core/CompileNew.go b/src/core/CompileNew.go
index 6d2ae30..c4b74bf 100644
--- a/src/core/CompileNew.go
+++ b/src/core/CompileNew.go
@@ -49,6 +49,6 @@ func (f *Function) CompileNew(root *expression.Expression) (types.Type, error) {
 	f.BeforeCall()
 	f.Label(asm.CALL, asm.Label{Name: "mem.alloc", Type: asm.FunctionLabel})
 	f.AfterCall(f.CPU.Input[:1])
-	f.Dependencies = append(f.Dependencies, alloc)
+	f.Dependencies.Add(alloc)
 	return &types.Pointer{To: typ}, nil
 }
diff --git a/src/core/EvaluateDot.go b/src/core/EvaluateDot.go
index 3bc55c2..bed4420 100644
--- a/src/core/EvaluateDot.go
+++ b/src/core/EvaluateDot.go
@@ -76,7 +76,7 @@ func (f *Function) EvaluateDot(expr *expression.Expression) (eval.Value, error)
 	function, exists := f.All.Functions[label]
 
 	if exists {
-		f.Dependencies = append(f.Dependencies, function)
+		f.Dependencies.Add(function)
 
 		value := &eval.Label{
 			Typ: types.AnyPointer,
diff --git a/src/core/EvaluateToken.go b/src/core/EvaluateToken.go
index 0b1aa30..991089e 100644
--- a/src/core/EvaluateToken.go
+++ b/src/core/EvaluateToken.go
@@ -46,7 +46,7 @@ func (f *Function) EvaluateToken(t token.Token) (eval.Value, error) {
 		function, exists := f.All.Functions[uniqueName]
 
 		if exists {
-			f.Dependencies = append(f.Dependencies, function)
+			f.Dependencies.Add(function)
 
 			value := &eval.Label{
 				Typ: types.AnyPointer,
diff --git a/src/core/Function.go b/src/core/Function.go
index 32de2cf..e38cbc7 100644
--- a/src/core/Function.go
+++ b/src/core/Function.go
@@ -4,6 +4,7 @@ import (
 	"git.urbach.dev/cli/q/src/dll"
 	"git.urbach.dev/cli/q/src/fs"
 	"git.urbach.dev/cli/q/src/register"
+	"git.urbach.dev/cli/q/src/set"
 	"git.urbach.dev/cli/q/src/token"
 )
 
@@ -18,7 +19,7 @@ type Function struct {
 	Body         token.List
 	Input        []*Parameter
 	Output       []*Parameter
-	Dependencies []*Function
+	Dependencies set.Ordered[*Function]
 	DLLs         dll.List
 	Err          error
 	deferred     []func()
diff --git a/src/readme.md b/src/readme.md
index 63ab66d..83641ce 100644
--- a/src/readme.md
+++ b/src/readme.md
@@ -24,6 +24,7 @@
 - [riscv](riscv) - RISCV implementation (w.i.p.)
 - [scanner](scanner) - Scanner frontend used by `build`
 - [scope](scope) - Defines a `Scope` used for code blocks
+- [set](set) - Generic set implementation
 - [sizeof](sizeof) - Calculates the byte size of numbers
 - [token](token) - Converts a file to tokens with the `Tokenize` function
 - [types](types) - Type system
diff --git a/src/set/Ordered.go b/src/set/Ordered.go
new file mode 100644
index 0000000..bc7caa5
--- /dev/null
+++ b/src/set/Ordered.go
@@ -0,0 +1,33 @@
+package set
+
+import (
+	"iter"
+	"slices"
+)
+
+// Ordered is an ordered set.
+type Ordered[T comparable] struct {
+	values []T
+}
+
+// Add adds a value to the set if it doesn't exist yet.
+// It returns `false` if it already exists, `true` if it was added.
+func (set *Ordered[T]) Add(value T) bool {
+	if slices.Contains(set.values, value) {
+		return false
+	}
+
+	set.values = append(set.values, value)
+	return true
+}
+
+// All returns an iterator over all the values in the set.
+func (set *Ordered[T]) All() iter.Seq[T] {
+	return func(yield func(T) bool) {
+		for _, value := range set.values {
+			if !yield(value) {
+				return
+			}
+		}
+	}
+}